1. G040292-00-D L-Bus Proposal CDS Meeting, June 23, 2004 Paul Schwinberg, Daniel Sigg

2. G040292-00-D LIGO I2 Goal Eliminate the cross-connects used by EPICS controls Simplify the EMI retrofit Replace with design that can operate in low noise environment Mass-termination on backplane Single controller with serial interface Modern bus-type design for both analog and digital Clean up the power supplies Locally regulated Support of legacy boards

3. G040292-00-D LIGO I3 Pros Drastic reduction of inter-system cabling Isolated power supplies Reduce susceptibility to EMI problems and noise injection Reduce documentation headaches because boards and interfacing go together Modifications are easier (new boards dont require re-cabling) Going forth and back between two designs is straight forward Better testing (boards AND subsystems can be fully tested in the shop without a custom rig) Support for loading and storing a digital word Sound infrastructure for advanced LIGO?

4. G040292-00-D LIGO I4 Cons Increased complexity (nothing is simpler than a cable!) Custom scheme of mass-termination Requires a commitment/Are we locked in? Requires a lot of individual interfacing for legacy boards

5. G040292-00-D LIGO I5 Basic Layout

6. G040292-00-D LIGO I6 Analog Backplane 16 lines of analog readbacks Each board selects one line Single ADC on controller board that operates at 2048 Hz (16 lines x 16 addresses x 16 Hz) GPS synchronized 4 analog addresses for multiplexing 16 analog readbacks on each board 8 analog control lines Used by boards that need to adjust voltages during running Typically DACs are on the user board

7. G040292-00-D LIGO I7 Digital Backplane Modern memory mapped architecture Multiplexed 16 bit address/16 bit data Boards typically use a 8 bit board identification Up to 128 words can be used locally Simple bus interface Address strobe/write indicator/data latch Low speed to minimize EMI problems Supports zero activity during science running Separate power supply

8. G040292-00-D LIGO I8 Power Supplies Voltages: +5V at 1A/board, digital, linear post-regulation ±5V at 1A/board, analog, linear post-regulation ±15V at 0.5A/board, analog, linear post-regulation ±24V at 1A/board, unregulated, use for local post-regulation Voltage monitoring ± 5% tolerance On/off switch

9. G040292-00-D LIGO I9 Form Factor Eurocrate 6U height, 220 mm depth (60 mm deeper than current boards) Full (21 slots) and half (10 slots) backplanes EMI compliant enclosure Support of legacy boards through 60 mm interface adapter Stand-alone chassis Everything goes… (Field module)

10. G040292-00-D LIGO I10 Software Dumb controller Supports reads, writes and read-modify-writes Supports 16 Hz data dump of analog readbacks Simple protocol to host computer (command, payload, return) Host computer provides EPICS and DAQ interface Runs EPICS database Talks to controller to set data values based on EPICS commands and to update readbacks Implements data dump to DAQ system to avoid EDCU bottleneck and maintain timing information

11. G040292-00-D LIGO I11 Plan Prototype by end of year (optimistically) Estimated costs: 10K-15K (buy crate, develop backplane, build power supply, develop controller, develop 1 user board and write software) Support of high density SMD components in EE shop(?): ~15K Support for EPROM/GAL/etc. burner in EE shop(?): ~5K Decision of go-ahead before LHO EMI retrofit is set into motion and depending on prototype results